industrial engineering

1. Project scheduling and
Maintenance
management
UNIT VI

2. Introduction
 Network analysis is one of the important tools for project
management.
 Whether major or minor a project has to be completed in a definite
time & at a definite cost.
 The necessary information of any particular data can be represented
as a project network.
 These techniques are very useful for planning, scheduling and
executing large-time bound projects involving careful co-ordination
of variety of complex and interrelated activities

3. Network Analysis

4. Objectives of network analysis
 Helpful in planning
 Inter-relationship of various activities
 Cost control
 Minimisation of maintenance time
 Reduction of time
 Control on idle resources
 Avoiding delays, interruptions, etc

5. Applications of network analysis
 Planning, scheduling, monitoring and control of
large and complex projects.
 Construction of factories, highways, building,
bridges, cinemas etc.
 Helpful to army for its missile development.
 Assembly line scheduling
 Installation of computers and high tech
machineries
 To make marketing strategies

6. Methodology Involved in Network
Analysis
Describing the Project
Diagramming the network
Estimating the time of completion
Deterministic
estimates
Probabilistic
estimates
Monitoring the project progress

7. Key terminology
 Activity : All projects may be viewed as composed of activities.
It is the smallest unit of work consuming both time & resources
that project manager should schedule & control.
 An activity is represented by an arrow in network diagram
The head of the arrow shows sequence of
activities.

8.  Classification of activities
 Predecessor activity: Activities that must be completed
immediately prior to the start of another activity are called
predecessor activities.
 Successor activity : activities that cannot be started until one or
more of other activities are completed but immediately succeed
them are called successor activities.
 Concurrent activities: activities that can be accomplished together
are known as concurrent activities.
 Dummy activity: An activity which does not consume any resource
but merely depicts the dependence of one activity on other is called
dummy activity. It is introduced in a network when two or more
parallel activities have the same start and finish nodes.

9.  Event:
 The beginning & end of an activities are called as events .
 Events are represented by numbered circles called nodes.
i j
Event
start
Event
finish

10. Types of Events
 Merge event
 Burst event
 Merge & Burst Event

11. Path & Network
 An unbroken chain of activity arrows connecting the initial event to
some other event is called a path.
 A network is the graphical representation of logically & sequentially
connected arrows & nodes representing activities & events of a
project . It is a diagram depicting precedence relationships between
different activities.

12. Key terminology continued…

18. Guidelines for Network
Construction
 A complete network diagram should have one stand point & one
finish point.
 The flow of the diagram should be from left to right.
 Arrows should not be crossed unless it is completely unavoidable.
 Arrows should be kept straight & not curved or bent.
 Angle between arrows should as large as possible.
 Each activity must have a tail or head event.. No two or more
activities may have same tail & head events.
 Once the diagram is complete the nodes should be numbered from
left to right. It should then be possible to address each activity
uniquely by its tail & head event.

19. Stages for project management
 Project planning stages : In order to
visualize the sequencing or precedence
requirements of the activities in a project, it
is helpful to draw a network diagram.
 Scheduling stage : Once all work
packages have been identified and given
unique names or identifiers, scheduling of
the project is required

20.  Project control stage :
Project control refers to evaluating
actual progress against the plan. If
significant differences are observed, then
the scheduling and resources allocation
decisions are changed to update and
revise the uncompleted part of the project

21. Advantages of PERT/CPM
 Planning & controlling projects
 Flexibility
 Designation of responsibilities
 Achievement of objective with least cost
 Better managerial control

22. Limitations of PERT /CPM
 Network diagrams should have clear starting & ending points , which
are independent of each other which may not be possible in real life.
 Another limitation is that it assumes that manager should focus on
critical activities.
 Resources will be available when needed for completion for an an
activity is again unreal.

23. Difficulties
 Difficulty in securing realistic time estimates.
 The planning & implementation of networks requires trained staff.
 Developing clear logical network is troublesome.

24. Example
Activity Predecessor
activity
A none
B none
C A
D A
E B
F C
G D & E
1
3
2
5
4
6
A
B
C
D
E
F
G

25. Draw the network diagram for the following
Activity Predecessor
activity
A none
B A
C A
D B
E C
F D ,E

26. 1 2
3
4
5 6
A
B
C
D
E
F

27. Critical path
 Those activities which contribute directly to the overall duration of
the project constitute critical activities, the critical activities form a
chain running through the network which is called critical path.
 Critical event : The slack of an event is the difference between the
latest & earliest events time. The events with zero slack time are
called as critical events.
 Critical activities : The difference between latest start time &
earliest start time of an activity will indicate amount of time by which
the activity can be delayed without affecting the total project
duration. The difference is usually called total float. Activities with 0
total float are called as critical activities

28. Critical path
 The critical path is the longest path in the network from the starting
event to ending event & defines the minimum time required to
complete the project.
 The critical path is denoted by darker or double lines.

29. Fulkerson’s Rule for Numbering
the Events

32. Difference between PERT & CPM
PERT
A probability model with
uncertainty in activity
duration . The duration of
each activity is computed
from multiple time estimates
with a view to take into
account time uncertainty.
It is applied widely for
planning & scheduling
research projects.
PERT analysis does not
usually consider costs.
CPM
A deterministic model with well
known activity times based upon the
past experience.
It is used for construction projects &
business problems.
CPM deals with cost of project
schedules & minimization.

33. PERT
PERT is designed for scheduling complex projects that
involve many inter-related tasks. it improves
planning process because:
1. It forms planner to define the projects various
components activities.
2. It provides a basis for normal time estimates & yet
allows for some measure of optimism or pessimism
in estimating the completion dates.
3. It shows the effects of changes to overall plans they
contemplated.
4. It provides built in means for ongoing evaluation of
the plan.

34. ESTIMATING ACTIVITY TIMES
 Optimistic time ( t0 ) : is that time estimate of an
activity when everything is assumed to go as per plan.
In other words it is the estimate of minimum possible
time which an activity takes in completion under ideal
conditions.
 Most likely time ( tm ) : the time which the activity will
take most frequently if repeated number of times.
 Pessimistic time ( tp) : the unlikely but possible
performance time if whatever could go wrong , goes
wrong in series. In other words it is the longest time
the can take.

35. EXPECTED TIME
 The times are combined statically to develop the expected
time te .
te = to + 4tm + tp
6
Standard deviation of the time of the time required to
complete the project
St = tp - to
6
Variance Vt = St × St

36. STEPS INVOLVED IN PERT
 Develop list of activities.
 A rough network for PERT is drawn.
 Events are numbered from left to right.
 Time estimates for each activity are obtained.
 Expected time for each activity is calculated : to+4tm+tp / 6
 Using these expected times calculate earliest & latest finish
& start times of activities.
 Estimate the critical path.
 Using this estimate compute the probability of meeting a
specified completion date by using the standard normal
equation
Z = Due date – expected date of completion
standard deviation of critical path

40. Books for numerical practices
 INDUSTRIAL ENGINEERING & MANAGEMENT by
PRAVIN KUMAR, PEARSON
 INDUSTRIAL ENGINEERING AND PRODUCTION
MANAGMENT by MARTAND TELSANG, S. CHAND &
COMPANY
 INDUSTRIAL ENGINEERING AND MANAGEMENT by
RAVI SHANKAR, GALGOTIAPUBLICATIONS

41. Maintenance Planning

42. Maintenance
 All actions necessary for retaining an item,
or restoring to it, a serviceable condition,
include servicing, repair, modification,
overhaul, inspection and condition
verification
 Increase availability of a system
 Keep system’s equipment in working order

43. Purpose of Maintenance
 Attempt to maximize performance of
production equipment efficiently and
regularly
 Prevent breakdown or failures
 Minimize production loss from failures
 Increase reliability of the operating
systems

44. Principle Objectives in
Maintenance
 To achieve product quality and customer
satisfaction through adjusted and serviced
equipment
 Maximize useful life of equipment
 Keep equipment safe and prevent safety
hazards
 Minimize frequency and severity of interruptions
 Maximize production capacity – through high
utilization of facility

45. Problems in Maintenance
 Lack of management attention to maintenance
 Little participation by accounting in analyzing
and reporting costs
 Difficulties in applying quantitative analysis
 Difficulties in obtaining time and cost estimates
for maintenance works
 Difficulties in measuring performance

46. Maintenance Objectives
 Must be consistent with the goals of
production (cost, quality, delivery, safety)
 Must be comprehensive and include
specific responsibilities

47. Maintenance Costs
 Cost to replace or repair
 Losses of output
 Delayed shipment
 Scrap and rework

48. Types of Maintenance
 Maintenance may be classified into four
categories:
 Corrective or Breakdown maintenance
 Scheduled maintenance
 Preventive maintenance
 Predictive (Condition-based) maintenance

49. Corrective or Breakdown
Maintenance
 Corrective or Breakdown maintenance implies
that repairs are made after the equipment is
failed and can not perform its normal function
anymore
 Quite justified in small factories where:
 Down times are non-critical and repair costs are less
than other type of maintenance
 Financial justification for scheduling are not felt

50. Disadvantages of Corrective
Maintenance
 Breakdown generally occurs inappropriate times
leading to poor and hurried maintenance
 Excessive delay in production & reduces output
 Faster plant deterioration
 Increases chances of accidents and less safety for
both workers and machines
 More spoilt materials
 Direct loss of profit
 Can not be employed for equipments regulated by
statutory provisions e.g. cranes, lift and hoists etc

51. Scheduled Maintenance
 Scheduled maintenance is a stitch-in-time
procedure and incorporates
 inspection
 lubrication
 repair and overhaul of equipments
 If neglected can result in breakdown
 Generally followed for:
 overhauling of machines
 changing of heavy equipment oils
 cleaning of water and other tanks etc.

52. Preventive Maintenance
 Principle – “Prevention is better than cure”
 Procedure - Stitch-in-time
 It
 locates weak spots of machinery and equipments
 provides them periodic/scheduled inspections and
minor repairs to reduce the danger of unanticipated
breakdowns

53. Advantages
 Advantages:
 Reduces break down and thereby down time
 Lass odd-time repair and reduces over time of
crews
 Greater safety of workers
 Lower maintenance and repair costs
 Less stand-by equipments and spare parts
 Better product quality and fewer reworks and
scraps
 Increases plant life
 Increases chances to get production incentive
bonus

54. Predictive (Condition-based)
Maintenance
 In predictive maintenance, machinery conditions
are periodically monitored and this enables the
maintenance crews to take timely actions,
such as machine adjustment, repair or overhaul
 It makes use of human sense and other sensitive
instruments, such as
 audio gauge, vibration analyzer, amplitude meter,
pressure, temperature and resistance strain gauges
etc.

55. Predictive Maintenance (Contd.)
Unusual sounds coming out of a rotating
equipment predicts a trouble
An excessively hot electric cable predicts a
trouble
Simple hand touch can point out many
unusual equipment conditions and thus
predicts a trouble

56. Maintenance Costs
Maintenance
Commitment
Cost
Breakdown Cost

57. Maintenance Costs
Maintenance
Commitment
Cost
PM Cost
Breakdown Cost

58. Maintenance Costs
Maintenance
Commitment
Cost
PM Cost
Breakdown Cost
Total Maintenance Cost

59. Maintenance Costs
Maintenance
Commitment
Cost
PM Cost
Total Maintenance Cost
Breakdown Cost
Optimal